Another thing: James Cameron portrays nature on Pandora as almost benign. True, it is explained that the Pandoran atmosphere is lethal to humans and we see Jake having a few hairy moments with some exotic monsters but that's it.
We don't see carnivores hunt and kill herbivores, etc., like we see on Earth. We don't see the Na'vi with injuries or diseases. We don't see animal carcasses. We don't see parasites.
Here's a reminder how savage nature really is.
A young cheetah is feeling thirsty and takes a drink. Big mistake! A crocodile woke up hungry that morning, and fancied a cheetah steak, done rare …
https://www.youtube.com/watch?v=A-8l-7guF84